1) Make the crust: Preheat oven to 350 degrees.

2) Combine graham cracker crumbs, butter, sugars, salt, and cinnamon in bowl. Firmly press mixture into bottom and up sides of a deep, 9 1/2-inch pie dish.

3) Bake until firm, 8 to 10 minutes.

4) Remove from oven, and sprinkle bittersweet chocolate over bottom of crust. Return to oven to melt chocolate, about 1 minute.

5) Spread chocolate in a thin layer on bottom and up sides.

6) Let cool on a wire rack. Reduce oven temperature to 325 degrees.

7) Make the filling: In a large heatproof bowl set over a pot of simmering water, melt semisweet chocolate and butter, stirring until smooth.

8) Remove from heat.

9) Mix pumpkin, milk, brown sugar, eggs, cornstarch, vanilla, salt, cinnamon, ginger, nutmeg, and a pinch of cloves in a medium bowl.

10) Whisk 1/3 pumpkin mixture into chocolate mixture.

11) Whisk in remaining pumpkin mixture until completely incorporated.

12) Transfer pie dish to a rimmed baking sheet, and pour pumpkin mixture into crust.

13) Bake until center is set but still a bit wobbly, 55 to 60 minutes.

14) Let cool in pie dish on a wire rack. Refrigerate until well chilled, at least 8 hours (preferably overnight). Before serving, drizzle melted milk chocolate on top.

15) Serve immediately.